linux-kernel - [PATCH v4 3/4] x86/smpboot: moves x86_topology to static initialize and truncate

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Message-ID: <20250706030636.397197-4-me@linux.beauty>
Date: Sun,  6 Jul 2025 11:06:31 +0800
From: Li Chen <me@...ux.beauty>
To: Li Chen  <me@...ux.beauty>," Thomas Gleixner "<tglx@...utronix.de>," Ingo Molnar "<mingo@...hat.com>," Borislav Petkov "<bp@...en8.de>," Dave Hansen "<dave.hansen@...ux.intel.com>,<x86@...nel.org>," H . Peter Anvin "<hpa@...or.com>," Rafael J . Wysocki "<rafael.j.wysocki@...el.com>," Peter Zijlstra "<peterz@...radead.org>," Sohil Mehta "<sohil.mehta@...el.com>," Brian Gerst "<brgerst@...il.com>," Patryk Wlazlyn " <patryk.wlazlyn@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Li Chen <chenl311@...natelecom.cn>,
	K Prateek Nayak <kprateek.nayak@....com>,
	Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>
Subject: [PATCH v4 3/4] x86/smpboot: moves x86_topology to static initialize and truncate

From: Li Chen <chenl311@...natelecom.cn>

The #ifdeffery and the initializers in build_sched_topology() are just
disgusting.

Statically initialize the domain levels in the topology array and let
build_sched_topology() invalidate the package domain level when NUMA in
package is available.

Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Li Chen <chenl311@...natelecom.cn>
---
 arch/x86/kernel/smpboot.c | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 6e36306632792..cd70e5322462a 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -478,32 +478,30 @@ static int x86_cluster_flags(void)
  */
 static bool x86_has_numa_in_package;
 
-static struct sched_domain_topology_level x86_topology[6];
-
-static void __init build_sched_topology(void)
-{
-	int i = 0;
-
-	x86_topology[i++] = SDTL(cpu_smt_mask, cpu_smt_flags, SMT);
+static struct sched_domain_topology_level x86_topology[] = {
+	SDTL(cpu_smt_mask, cpu_smt_flags, SMT),
 #ifdef CONFIG_SCHED_CLUSTER
-	x86_topology[i++] = SDTL(cpu_clustergroup_mask, x86_cluster_flags, CLS);
+	SDTL(cpu_clustergroup_mask, x86_cluster_flags, CLS),
 #endif
 #ifdef CONFIG_SCHED_MC
-	x86_topology[i++] = SDTL(cpu_coregroup_mask, x86_core_flags, MC);
+	SDTL(cpu_coregroup_mask, x86_core_flags, MC),
 #endif
-	/*
-	 * When there is NUMA topology inside the package skip the PKG domain
-	 * since the NUMA domains will auto-magically create the right spanning
-	 * domains based on the SLIT.
-	 */
-	if (!x86_has_numa_in_package)
-		x86_topology[i++] = SDTL(cpu_cpu_mask, x86_sched_itmt_flags, PKG);
+	SDTL(cpu_cpu_mask, x86_sched_itmt_flags, PKG),
+	{ NULL },
+};
 
+static void __init build_sched_topology(void)
+{
 	/*
-	 * There must be one trailing NULL entry left.
+	 * When there is NUMA topology inside the package invalidate the
+	 * PKG domain since the NUMA domains will auto-magically create the
+	 * right spanning domains based on the SLIT.
 	 */
-	BUG_ON(i >= ARRAY_SIZE(x86_topology) - 1);
+	if (x86_has_numa_in_package) {
+		unsigned int pkgdom = ARRAY_SIZE(x86_topology) - 2;
 
+		memset(&x86_topology[pkgdom], 0, sizeof(x86_topology[pkgdom]));
+	}
 	set_sched_topology(x86_topology);
 }
 
-- 
2.49.0